Shrubs, 10-80 cm. Stems 1-5+, erect, unarmed, pannose but for floccose or glabrescent streaks. Leaves: primaries lanceolate to spatulate, 5-40 (× 2-6) mm, tomentose to sericeous; secondaries similar, smaller. Heads 3-8. Peduncles 5-25 mm. Involucres turbinate to cylindric, 6-12 mm. Phyllaries 4, oblong to lanceolate. Florets 4; corollas cream to bright yellow, 7-15 mm. Cypselae 3-5 mm, glabrous or hirsute; pappi of 100-150 bristles 6-11 mm. 2n = 60, 62, 90, 120.
Flowering spring-fall. Sagebrush scrub, pinyon-juniper woodlands, yellow-pine forests; 400-3300 m; B.C.; Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., Utah, Wash., Wyo.
Common Name: spineless horsebrush
Duration: Perennial
Nativity: Native
Lifeform: Shrub
General: Shrub, 0.2-0.8 m (0.7-2.6 ft) tall; stems solitary to few, erect, unarmed, much-branched, branches and twigs covered with a dense, felt-like tomentum, interspersed with somewhat glabrous streaks.
Leaves: Cauline, alternate, simple, usually with clusters of secondary leaves in the axils of the primary ones, primary blades linear, lanceolate, or oblanceolate, 0.5-4 cm long, 2-6 mm wide, secondary blades smaller, surfaces tomentose to silky pubescent, margins entire, apex sometimes tipped with a minute spine; blades sessile or nearly so.
Flowers: Heads 3-8, arranged in cyme-like clusters; involucre top- shaped to cylindric, 6-10 mm long; involucral bracts 4, oblong to lanceolate, tomentose; disk flowers only, 4, cream to bright yellow.
Fruits: Achene, 3-5 mm long, glabrous or densely silky pubescent; pappus of numerous white to tan hair-like bristles.
Ecology: Found in dry, open habitats, plains, foothills, mountains from 5,000-10,500 ft (1524-3200 m), flowers July-October.
Distribution: Apache, Coconino, Mohave, Navajo, and Pima counties; western Canada, western and southwestern U.S.
Notes: A highly drought-tolerant plant, Tetradymia canescens is also fire-adapted; although top-killed by fire, it sprouts from the root crown and also produces a prolific seed crop. It is toxic to sheep.
Ethnobotany: The Hopi use a decoction of the leaf and root to shrink the uterus and stop discharge after birth. The Navajo use the plant as a ceremonial emetic and as a cold remedy, and also make a yellow dye from the flowers.
Editor: Springer et al. 2011
